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  • Author or Editor: Ali Bechrifa x
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Abstract

Phosphobaryum carbonate hydroxyapatites Ba10(PO4)6(OH)(2−2x)(CO3)x with 0 ≤ x ≤ 1, were synthesized in this study by solid gas reaction at a high temperature. Carbonate content was determined by thermogravimetric analysis and X-ray diffraction. The heat of the solution in a 3 wt% nitric acid solution was measured at 298 K using an isoperibol calorimeter. The combination of the enthalpies of solution with the enthalpies of formation of the reactants allowed us to determine the standard enthalpies of formation of the studied apatites. The result showed a decrease in formation enthalpy with the carbonate amount introduced in the lattice, suggesting an increase in stability of these compounds as the ratio of the substitution increases.

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Abstract

“A” type phosphostrontium carbonate hydroxyapatites, having the general formula Sr10(PO4)6(OH)(2−2x)(CO3)x with 0 ≤ x ≤ 1, were synthesised by solid gas reaction at high temperature. The samples were characterised by X-ray diffraction and infrared spectroscopy. Analysis of carbonate was achieved by coulometry and Rietveld refinement of the structure. Using an isoperibol calorimeter, the heat of solution of these products was measured at 298 K in 9 wt% nitric acid solution. Thermochemical cycle was proposed and complementary experiences were performed to reach the standard enthalpies of formation of these compounds. The results showed a decrease of the enthalpy of formation with the amount of carbonate introduced in the lattice, suggesting an increase of stability due to this kind of substitution.

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